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An Open and Shut Case: The Invention of the Zipper

A typical morning for me (Ray) goes something like this: I get up, shower, shave, and get dressed for work. I button my shirt, zipper my pants, tighten my belt, and tie my shoelaces. I then go to the kitchen to make my lunch. I put a sandwich and snacks in Ziploc bags, throw them in my canvas lunch bag, and close the zipper.

Before I head out the door, I put on a light jacket and zip it up. When I get to work, I go through security where I unzip my lunch bag, show the guard the contents, and then zipper it back up.

Some days, I get calls asking me to test a piece of equipment. I throw my tools in a backpack and close the zipper. When I get to the work location, I unzip the backpack to get to my tools.

Do you see a recurring theme? Devices such as buttons, belts, laces, and zippers are actually tools that are known as fasteners. They are very useful, and you probably use them more than you think! This issue’s column will focus on the invention of one of these devices, known as the zipper.

The World Before the Zipper

As already mentioned, zippers fit into a class of mechanical devices called fasteners. A fastener is used to connect two or more things together; that is, to fasten them to one another. If you think about using a zipper, you usually think about an article of clothing such as pants or a coat, and rightly so. The zipper fastens two pieces of cloth together. It also provides a simple way to unfasten the same two pieces. That is the beauty of the zipper. It is fast, efficient, and can be used over and over again to repeatedly open and close things.

Before the zipper was invented, what kinds of fasteners did people use? In biblical times, men and women wore tunics. Tunics were garments made from two pieces of material that were joined together by a seam at waist level. A tunic was held up against the wearer’s waist by a girdle made from leather or other coarse material. The girdle, which was akin to what we would know as abelt, served as a kind of fastener.

If a man had to work or run, he would pull up his tunic and tuck it into the girdle to give him greater freedom of movement for his legs. This was called girding up one’s loins. If you do a word search in the Bible, you will find the word gird appearing numerous times throughout Scripture. It often means “to fasten” something to a person, whether it be clothes or a weapon.

Another piece of clothing that was often worn, especially during cold weather, was a cloak. A cloak was a piece of cloth that had slits in it for arms. It was worn over the top of a tunic. Because of their designs, neither the tunic nor the cloak required any kind of special fastener to hold things together. Wearing them was simply a matter of sliding the garment on and adjusting the girdle.

About 2800 BC, people began to adorn clothes with ornaments and seals made from seashells that were carved into different shapes. These served no real functional purpose that we know of other than fashion. But that started to change in the 13th century.

The textile industry grew and matured in Europe. Clothing fashions began to change, and garments became increasingly snug. Buttons, and their associated buttonholes, were used to fasten clothes together.

Buttons had some great advantages: They were simple to use and easy to fix or replace. The first European buttons became status symbols. The larger and more intricate a man’s buttons were, the more power and prestige he was given. Gold and silver buttons were proudly displayed by nobility. Specialized button craftsmen were hired to manufacture increasingly ornate buttons that included carvings and paintings on them. Things started to get a bit out of hand, with some men having buttons nearly the size of dinner plates on their jackets!

The Invention of the Zipper

Although buttons were easy to use, there were times when better ways to fasten clothing together were needed. Depending on how the buttons were arranged on one’s clothes, the simple act of sitting down could be cumbersome and could damage the upholstery on furniture. Also, buttons do not provide a very tight seal, which is important in cold climates.

In 1851, inventor Elias Howe (who also invented the sewing machine), received a patent for a device called an “Automatic Continuous Clothing Closure.” This would be the first version of what we commonly refer to as a zipper today. Although Howe invented this device, the popularity of the sewing machine occupied so much of his time and effort that he never pursued the development of a market for his invention.

Over forty years would go by with no zippers until another inventor, Whitcomb Judson, developed a similar device he called the “Clasp Locker.” Unlike Howe, Whitcomb decided to market his invention. He formed the Universal Fastener Company to manufacture clasp lockers. Unfortunately, in spite of his best efforts, his product did not capture the public’s attention and never really took off.

All was not lost, however. One of Judson’s engineers, a Swedish gentleman named Gideon Sundback, began working on different designs for the clasp locker. It was Sundback who would create what we would consider to be the first modern zipper, which Sundlack named the “Separable Fastener.” In addition to the “Separable Fastener,” he also invented a machine that could manufacture the device, making several hundred per day.

One of the first buyers for Sundback’s invention was the B.F. Goodrich Company. They wanted to use the device to act as a fastener for a new design they had for rubber boots. It was the people at Goodrich that coined the name “zipper.”

The Anatomy of a Zipper

If you have ever looked at a zipper, you know that they seem to be pretty simple devices. But there is more to them than first meets the eye! In general, a zipper has 12 parts. They are:

•Top Tape Extension: fabric that extends beyond the top of the zipper

•Top Stop, or Bridge Stop: used at the top of the zipper to keep it from separating

•Slider: the device that moves up and down the actual chain

•Pull Tab: the part of the slider that moves up and down to open and close

•Bottom Stop: a device at the bottom of the zipper to keep it from separating

•Bottom Tape Extension: fabric that extends below the bottom of the zipper

•Single Tape Width: the width of one half of the zipper fabric

•Insertion Pin: a device used on a separating zipper (like the kind on a jacket) that allows a person to join the two sides of the zipper together.

•Retainer Box: an end stop at the bottom of some zippers

•Reinforcement Film: additional fabric to add reinforcement strength at the bottom of the zipper

Try taking a magnifying glass sometime and seeing how many of the zipper parts you can identify!

Types of Zippers

Because of the utility of zippers, there are many different designs to address specific applications. Some examples are:

•Closed Bottom: found on a pair of pants

•Separating: found on jackets and meant to come apart or separate

•Two-Way Separating: found on some types of jackets

•Two-Way Coverall: found on coveralls to allow zipping and unzipping from either the top or bottom

•Two-Way Luggage/Backpack: found on soft-cover suitcases that allow opening on the top like a lid

In 1956, the British invented a special zipper that was able to seal storage bags for military equipment that was sensitive to moisture. In 1958, NASA contracted the manufacturer to make a higher strength version for the Mercury and Gemini space programs. The zippers worked so well that an even stronger zipper was developed for the Apollo space program. Military forces all over the world use these specialty zippers, as do scuba divers (on their wetsuits) and some fire-brigade personnel. These zippers are both waterproof and airtight.

Believe it or not, there are also fireproof zippers used on the protective clothing that firefighters wear, and chemical-resistant zippers are used on the protective clothing worn by workers in some chemical plants!

Zipper Engineering

What makes a good zipper? Mostly, it must be strong! There are actually six engineering measurements that are made to determine just how strong a zipper is. Who would have thought that! The actual test descriptions get a little complicated to explain, but see if you can get an idea from the names of the tests as to what they are trying to measure:

•Crosswise Strength

•Vertical Tensile Strength of the Top Stop

•Bottom Stop Tearing Strength

•Tensile Strength of the Box

•Slide Lock Strength

•Overall Strength of the Slider

For a more detailed description of these tests, with pictures, check out the following website: www.teonline.com/knowledge-centre/ zipper.html.

Variations on the Theme

It seems that there is always a need to open and close things repeatedly and quickly. The zipper does a very good job of that, but there are other inventions designed to do the same thing.

Have you ever packed a lunch to take on a trip? You may have used a Ziploc bag to keep your sandwich fresh. Ziploc bags are made of plastic and have male and female sides that lock together. Originally, Ziploc bags had only one seal, but now many have two. The seals are very tight and can be waterproof. Try doing that with buttons!

Another invention you are probably familiar with is Velcro. Velcro is usually made from nylon and has two sides. One side is called the hook side (it looks like a forest made up of tiny mushrooms). The other side is called the loop side (it looks like chain stitching made from nylon threads). When you press the two sides together, the hooks and the loops lock together to fasten the material.

Ray and Gale Lawsonhave been homeschooling their three children since 1995. Ray holds a BS in Electrical Engineering from the Virginia Military Institute and is also a student, pursuing a Masters in Nuclear Engineering at the University of South Carolina. He works for Savannah River Nuclear Solutions, LLC. Gale holds a BS in Mechanical Engineering from the University of South Carolina and is a full-time mom and teacher. They are members of Breezy Hill Baptist Church in Graniteville, SC. Questions, comments, and suggestions are always welcome and can be e-mailed to them at [email protected] (Ray) or [email protected] (Gale).